Studies conducted over the previous funding period were aimed at examining vSub-mPFC modulation of the NAc and how this affects dopamine (DA) neuron activity, and how this is disrupted in the MAM rat model of schizophrenia. Using the MAM model of schizophrenia, we found that these rats show hyper-responsivity to amphetamine that correlates with an increase in the number of dopamine neurons firing (i.e., dopamine neuron population activity). Moreover, this increase Is due to increased drive from the ventral subiculum of the hippocampus (vSub); a region that also shows decreased parvalbumin interneuron labeling. Forthe next 5 years ofthis grant, we plan to focus on several unique findings made during the initial funding period. Specifically, we plan to focus on plasticity and interactions of the hippocampus/prefrontal cortex interactions within the nucleus accumbens, and to now include the amygdala into this interaction based on growing evidence of Its importance in schizophrenia; to test whether the increase in hippocampal activity is correlated with a loss of parvalbumin interneurons or instead to a decrease in parvalbumin expression; to examine novel treatments for schizophrenia using our animal model; and to examine whether peripubertal inten/ention can prevent the transition to schizophrenia, and conversely whether stress during this interval will exacerbate the schizophrenia-like pathological changes. This will be accomplished by the following specific aims: 1. Examine how afferent drive and synaptic plasticity is altered in the MAM model within the vSub-mPFCamygdala- NAc circuit; 2. Examine whether the increased vSub activity is due to loss of parvalbumin interneurons or decreased parvalbumin expression due to decreased interneuron drive, when this occurs in development, and if this can be reversed. 3. Examine potential novel treatments for schizophrenia based on restoration of function in the MAM model. 4. Examine whether peripubertal intervention can exacerbate or prevent the transition to experimental psychosis/pathophysiology in the MAM rat. We hope that this will provide novel information regarding the cellular dynamics underlying the pathological changes that occur In schizophrenia, novel targets for more effective treatment, and the potential for a preventive strategy.